In DAZ Studio how do I add a jpeg as a texture to a model?

To add a jpeg as a texture, you must go to the Surfaces Tab (usually on the right or go to VIEW à Tabs àSurfaces). On the left half of the Surfaces Tab, find the surface you wish to add a texture to. Highlight it. Unlike the scene tab, selections in the Surfaces Tab work independently. So if you have something selected in the scene tab, it is not necessarily selected in the Surfaces Tab and vice versa.

On the right half, you will see two little tabs, Basic and Advanced. To change the texture only, you can use either tab. The first selection on the tab, Color | Diffuse or Diffuse Color is where to add a jpg. To do this, click on the drop down bar or the drop down arrow to the right of the bar with the numbers. You should see a choice 'Browse for Image…' Click on this. In the new window that appears, browse to the jpg you want. Browse to the picture, select, and click 'Open.' You should now see the image on the primitive or figure.